The invention relates to an electromotor comprising a rotor part and a stator part, which parts are formed into a bearing system by means of oil-containing spiral groove bearings, whereby parts of the surface of the rotor part and of the stator part are provided with an oil barrier to counteract oil creepage from the bearings. The invention also relates to a method of manufacturing such an electromotor.
An electromotor of the type mentioned in the opening paragraph is known per se, for example, from United States patent specification U.S. Pat. No. 5,427,456. Said specification more particularly describes an electromotor which can suitably be used to drive a hard disk of a computer. The known motor comprises four spiral groove bearings, namely two axial bearings and two radial bearings. To prevent oil creepage from the bearings during operation of the motor, layers are provided, for example at an end portion of the rotor part, which counteract oil creepage. Such layers are commonly referred to as "oil barriers" and "Nyebar stop". Such oil barriers customarily comprise a mixture of fluoro compounds, such as perfluoroalkanes, which are embedded in a polymer matrix.
It has been found that in some respects the known electromotors are unsatisfactory. For example, if the motor is operated at a fixed speed for a prolonged period of time, oil migration from one spiral groove bearing to the other spiral groove bearing may occur. This may cause the first spiral groove bearing to run dry, thus causing damage to the motor.